import java.util.Arrays;

public class PriorityQueue {
    public int[] elem;
    public int usedSize;

    public PriorityQueue() {
        elem=new int[5];
    }
    /**
     * 建堆的时间复杂度：O(n)
     *
     * @param array
     */
    public void createHeap(int[] array) {
        for (int i = 0; i <array.length ; i++) {
            elem[i]=array[i];
            usedSize++;
        }
        for (int parent =(usedSize-1-1)/2 ; parent >=0 ; parent--) {
            shiftDown(parent,usedSize);
        }
    }

    /**
     *向下调整
     * @param root 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int root,int len) {
        int child=2*root+1;
        while (child<usedSize){
            if (child+1<usedSize&&elem[child]<elem[child+1]){
                child++;
            }
            if (elem[child]>elem[root]){
                swap(child,root);
                root=child;
                child=2*root+1;
            }else {
                break;
            }
        }
    }
    private void swap(int i,int j){
        int temp=elem[i];
        elem[i]=elem[j];
        elem[j]=temp;
    }
    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
    public void push(int val) {
        if (isFull()){
            elem=Arrays.copyOf(elem,2*elem.length);
        }
        elem[usedSize]=val;
        shiftUp(usedSize);
        usedSize++;
    }

    private void shiftUp(int child) {
    int parent=(child-1)/2;
    while (child>0){
        if (isFull()){
            elem= Arrays.copyOf(elem,2*elem.length);
        }
        if (elem[child]>elem[parent]){
            swap(child,parent);
            child=parent;
            parent=(child-1)/2;
        }else {
            break;
        }
    }
    }

    public boolean isFull() {
        return usedSize==elem.length;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */
    public void pollHeap() {
        if (isEmpty()){
            return;
        }
        swap(0,usedSize-1);
        usedSize--;
        shiftUp(usedSize);
    }

    public boolean isEmpty() {
        return usedSize==0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        if (isEmpty()){
            return -1;
        }
        return elem[0];
    }
    public void printHeap() {
        if (isEmpty()) {
            System.out.println("堆为空");
            return;
        }
        for (int i = 0; i < usedSize; i++) {
            System.out.print(elem[i] + " ");
        }
        System.out.println();
    }

}